JPS59146443A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve corrosion resistance by forming a ferromagnetic thin metallic film contg. oxygen on a non-magnetic base plate, and sticking a rust inhibitive agent consisting essentially of a benzothiazole compd. on said thin film. CONSTITUTION:The benzothiazole compd. refers to benzothiazole, 2-methylbenzothiazole, 2-benzothiazolone, etc. The rust inhibitive agent consists essentially of any among these benzothiazoles alone or a mixture composed of >=2 kinds thereof (more preferably contg. at least >=80%) and is added, if necessary, with a small amt. of an org. compd. except the benzothiazole compd., for example, naphthol, hydroquinone or the like. The rust inhibitive agent is effective if said agent is so formed as to exist on at least the surface, and in the inside, if possible, of a ferromagnetic thin film or to exist in the state of contacting with the boundary with the substrate on which the ferromagnetic thin film is formed. The adequate amt. thereof is about 0.5-500mg per m3 of the magnetic recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a ferromagnetic metal thin film magnetic recording medium with improved corrosion resistance in high humidity.

Structure of the conventional example and its problems Fe, Ni, Ni, A magnetic recording medium that is mainly composed of Co or an alloy thereof and is ferromagnetic and contains oxygen is suitable for high-density recording such as video signal recording. 0
．． Because it is as small as 5 μm, if it is left in high humidity environments, especially in environments where there are large temperature changes and condensation occurs, it is likely to cause corrosion on the surface, and once this corrosion has progressed to a certain extent,
Affects electromagnetic conversion characteristics and deteriorates practical characteristics such as head touch and abrasion resistance.

When suppressing this corrosion with a rust preventive agent, there are strict limitations on the thickness of the protective film that can be formed on the surface of the magnetic layer due to spacing loss between the head and the magnetic layer. There was a desire for a rust preventive agent that was sufficiently effective.

Ferromagnetic thin films that are mainly made of Fe, Ni, Co, or their alloys and contain oxygen have higher coercive force and superior corrosion resistance than thin films made of pure metals. In other words, known partially oxidized rust preventives (materials that exhibit a rust preventive effect) are not necessarily suitable, and when these rust preventives are actually applied, they have the opposite effect. Since it may accelerate corrosion, it became necessary to find a new material that is compatible with ferromagnetic thin films containing oxygen.

OBJECTS OF THE INVENTION The present invention provides a magnetic recording medium in which a rust preventive agent suitable for the ferromagnetic thin film described above is attached.

DESCRIPTION OF THE INVENTION As a result of various studies, the present inventors have discovered that a benzothiazole-based compound is suitable as a protective agent for ferromagnetic thin films containing oxygen. That is, the present invention provides a magnetic recording medium in which a ferromagnetic metal thin film containing oxygen is formed on a nonmagnetic substrate, in which a rust preventive agent containing a benzothiazole compound as a main component is attached to the ferromagnetic metal thin film. It is characterized by:

Examples of nonmagnetic substrates used include plastic films such as polyester film and polyimide film 1, metal plates such as aluminum plates and stainless steel plates, and inorganic plates such as glass plates. A layer of diagonal or vertical columnar crystals with a thickness of 0.05-0.
．． 5 μm Co, Fe-Ni, Co-Ni, Fe-Co
, Fe-Ni-Co, etc., and a single or multilayer ferromagnetic thin film containing 3 to 45% oxygen in atomic ratio to the magnetic metal. Apply rust agent.

Description of Examples Benzothiazole in the present invention includes benzothiazole, 2-methylbenzothiazole, 2-(p-aminophenyl)-6-methylbenzothiazole, 2-mercaptobenzothiazole, benzothiazoline, 2-benzothiazolone, etc. There is.

The rust preventive agent in the present invention is mainly composed of a single substance or a mixture of two or more of these compounds (preferably containing at least 80%), and optionally contains organic compounds other than benzothiazole compounds, such as It contains small amounts of naphthols, hydroquinones, acetophenones, quinones, etc.

These rust preventive agents exhibit their effects by being present at least on the surface of the ferromagnetic thin film, if possible inside, or in contact with the interface with the base on which the ferromagnetic thin film is formed. The appropriate amount is about 0.5 to 500 mg per m2 of magnetic recording medium. Specifically, the rust preventive agent is applied on the surface of the ferromagnetic thin film, either by itself or mixed with a film-forming agent such as a polymer compound, diluted with a solvent if necessary. Method,
A method of applying rust preventive vapor to the surface of a ferromagnetic thin film, and
When the magnetic recording medium is in the form of a tape, known means can be used, such as a method in which the magnetic recording medium is placed on the back surface of the medium and transferred onto the surface of the ferromagnetic thin film when the tape is rolled up. In addition to the rust preventive agent, it is also possible to use ordinary lubricants, antistatic agents, and other additives.

Next, specific examples of the present invention will be described.

A CoNi alloy (Ni content: 2Owt%) was continuously obliquely deposited (cutting the low incident angle component by 30° or less),
One was formed on an oxygen-containing CoNi ferromagnetic thin film with a thickness of 1000 Å (sample A), and the other was formed on a GoNi film that did not contain oxygen under the same conditions as above at a vacuum level of 5 × 10-6 Torr without introducing oxygen gas. A sample (sample B) on which a magnetic thin film was formed was prepared. As a result of measuring the amount of oxygen in the film mainly using Auger electron spectroscopy, the average amount of oxygen in the film of Sample A was 10% in terms of atomic ratio to Co and Ni, and that of Feed B was less than 1%. Ta. After applying and drying a rust preventive agent containing a penzothiazole-based compound as a main component dissolved in ethyl alcohol, acetone, toluene, etc. to the surface of these materials (the applied amount was adjusted to 10 to 100 mg/m2), The specimen was left in an atmosphere at a temperature of 50 degrees Celsius and a relative humidity of 90%, during which time it was periodically taken out and observed under a microscope to examine the state of rust formation. The results are shown in the table below.

From this result, for sample B, no effect was observed in any benzothiazole type. For sample A, benzothiazole, 2-methylbenzothiazole, 2-(P-aminophenyl)-6-methylbenzothiazole, and 2-mercaptobenzothiazole were 5
No rust occurred even after a week. Further, with benzothiazoline and 2-benzothiazolone, no rust was observed for up to 4 weeks, and although some rust occurred after 5 weeks, sufficient rust prevention results could be observed.

Effects of the Invention As described above, according to the present invention, a ferromagnetic metal thin film containing oxygen can have an excellent antirust effect.

Claims (1)

[Claims] A magnetic recording medium characterized in that a ferromagnetic metal thin film containing oxygen is formed on a nonmagnetic substrate, and a rust preventive agent containing a benzothiazole compound as a main component is adhered to the ferromagnetic metal thin film.